Molded plastic closures such as for use on containers for carbonated beverages and the like have met with extremely widespread acceptance in the marketplace. Commonly-assigned U.S. Pat. Nos. 4,378,893 and No, 4,343,754, disclose closures of this type, and highly efficient techniques for manufacture thereof. U.S. Pat. No. 4,497,765 discloses further techniques for manufacturing such closures, including manufacture of closures each having a tamper-indicating pilfer band. Each of the above-referenced patents is hereby incorporated by reference.
U.S. Pat. Nos. 4,938,370, and No. 4,978,017, both hereby incorporated by reference, each illustrate a plastic closure generally of the above type, with a tamper-indicating plastic band particularly configured for highly reliable and consistent tamper-indication. The pilfer band constructions disclosed in these two patents include pilfer bands which are at least partially detachably connected to an annular skirt portion of the closure, with a plurality of circumferentially spaced, inwardly extending projections provided for engagement with an annular locking ring of an associated container.
For some applications, it is desired that the pilfer band remain on the container after closure removal. To this end, a suitable fracturable connection is provided between the pilfer band and the skirt portion of the closure so that the pilfer band entirely separates from the skirt portion.
In contrast, for some applications (such as for returnable, reusable containers) it is desired that the pilfer band remain partially connected to the skirt portion of the closure, while portions of the band fracturably separate from the skirt portion to provide the desired visible indication of opening. For such applications, it is desirable to form the closure such that at least one portion of the pilfer band splits vertically, with the one or more band segments thus formed remaining joined to the skirt portion of the closure by at least one integral connector portion. U.S. Pat. No. 4,666,053, hereby incorporated by reference, illustrates one embodiment of such a closure, and a method of vertically scoring the closure pilfer band. U.S. patent application Ser. No. 07/958,014, filed Oct. 7, 1992, now U.S. Pat. No. 5,320,234, hereby incorporated by reference, illustrates a presently preferred configuration for such vertical scoring, including a pair of staggered vertical scores.
In practice, vertical scoring requires a sharp scoring blade to penetrate the periphery of the pilfer band of the closure to a precise, controlled depth (or all the way through the pilfer band) and to consistently form a small incision which can be repeatably cut. Experience has shown that the best results are achieved by holding the closure cap motionless on a cylindrical mandrel while moving a radially oriented scoring blade radially into and then out of the closure pilfer band.
In high-speed machinery, however, it is very difficult to have the closure cap remain motionless during scoring blade insertion and removal, especially if the machine is also configured to perform horizontal scoring for otherwise separating and distinguishing the pilfer band from the skirt portion of the closure cap. Moreover, mechanisms in which both the closure cap and the vertical scoring blade are in motion during insertion and removal generally cannot maintain the radial orientation of the blade and/or cannot achieve true radial insertion and removal of the blade. The resultant "digging"(i.e., non-radial) motion of the blade in the plastic can produce unsatisfactory scoring results.
In the above-referenced U.S. Pat. No. 4,666,053, the illustrated arrangement for effecting vertical scoring includes a spring-loaded, pivotally movable scoring blade. The spring-loaded blade is motionless until a closure cap, moving along a circular path, engages the tip of the blade. The moving closure engages and "picks up" the blade, causing it to pivot and score the cap. While the geometry of the blade and associated closure-moving carousel can be arranged to yield optimum blade-to-closure relative motion, the repeatability of the point of blade engagement on the closure is poor, resulting from closure cap and machine dimensional variations. Moreover, at higher speeds, the spring-return oscillating motion of the pivotal scoring blade becomes less repeatable because of bouncing, and variation in the point in which the blade is released to "fly back" to its initial, resting position.
The present invention is directed to a method and apparatus for effecting high-speed scoring, particularly vertical scoring, of a tamper-indicating plastic closure while achieving consistent and precise scoring and cutting of the closure.